Localization of the Cell-associated Phosphatase in Lysobacter enzymogenes

Abstract

Summary: In addition to an excreted phosphatase, Lysobacter enzymogenes produces a distinctly different alkaline phosphatase which remains associated with the cells. It is the only major phosphatase contained in the cells. Little enzyme activity is found in whole cells using the standard assay with p-nitrophenyl phosphate as the substrate, but maximum activity can be obtained after toluene or detergent treatment, or mechanical disruption of the cells. The phosphatase is not released from the cells by osmotic shock, or by treatment with MgCl2 or high LiCl concentrations. It is associated with the particulate fraction in cell-free extracts and detergents solubilize the enzyme from intact and broken cells. Separation of the inner and outer membranes of the cells by sucrose gradient centrifugation showed that most, if not all, of this phosphatase is located in the outer membrane.